Periodic Lateralized Epileptiform Discharges–A Critical Review

Abstract

It is the purpose of this review to critically consider and organize the literature dealing with the ephemeral electroencephalographic (EEG) pattern periodic lateralized epileptiform discharges (PLEDs). Although the retrospective nature of these studies limits their ability to discuss accurately the clinical and pathophysiological aspects of this EEG entity, the available data strongly emphasize stroke as the dominant etiology and its high association with seizures. Recent evidence, particularly from functional neuroimaging studies, strongly suggests that PLEDs might reflect a key pattern for focal hyperexcitability in the penumbra zone of ischemic stroke. The authors prefer to consider PLEDs as an EEG signature of a dynamic pathophysiological state in which unstable neurobiological processes create an ictal-interictal continuum, with the nature of the underlying neuronal injury, the patient's preexisting propensity to have seizures, and the co-existence of any acute metabolic derangements all contributing to whether seizures occur or not. This review underlines the need for further sophisticated prospective controlled studies implementing early continuous EEG monitoring in order to contribute to an understanding of the incidence, dynamics, and relevance of this pattern.

Nonconvulsive Status Epilepticus During Perioperative Period of Cerebrovascular Surgery

“…6) PLEDs characteristically appear in a hemisphere containing an acute unilateral forebrain lesion, which most commonly occurs in patients with CVD. 12,17,26) Although PLEDs may occur in fully conscious patients with epilepsia partialis continua, as well as negative motor seizures that mimic transient ischemic attack, the comatose or confusion states associated with PLEDs are generally accepted to be caused by NCSE. 2) In Case 1, the location of the highest amplitude of PLEDs was identical to the intracerebral hematoma location.…”

“…Therefore, this small hematoma was thought to be an epileptogenic lesion. The relationship between PLEDs and cerebral blood flow (CBF) and metabolism is well documented, 17,26) and blood flow changes have been shown to alter seizure threshold. 12) In addition, a reduction in threshold was found in patients who underwent CEA and developed seizures and PLEDs, which were ipsilateral to hyperperfusion-associated CEA.…”

Quantitative EEG for the Detection of Brain Ischemia

“…Regional changes, including a lack of delta or the presence of faster frequencies within 24 hours, correlate with a good outcome [23] while the persistence of unilateral prominent, continuous delta slowing or decreased alpha adds signifi cantly to clinical predictions of poor outcome [24]. Other specifi c patterns may also indicate poor prognosis, such as RAWOD (with up to 67% mortality) [13] or periodic lateralized epileptiform discharges (PLEDs) [25].…”

The Utility of EEG, SSEP, and Other Neurophysiologic Tools to Guide Neurocritical Care

“…1) or lateralized periodic discharges are electrographic injury patterns often present on surface EEG during an acute presentation from ischemic stroke, intracerebral hemorrhage, subdural hematoma, subarachnoid hemorrhage, malignancy, hypoxic-ischemic encephalopathy, encephalitis, posterior reversible encephalopathy syndrome, or other forms of acute brain injury, or one of these structural causes in association with superimposed metabolic encephalopathy [58]. The majority of patients with PLEDs on initial EEG either had a prior seizure or will go on to have future clinical seizures [59]. Accordingly, these patterns are often treated with antiseizure medication.…”